Messages in this thread | | | Date | Thu, 4 Dec 2014 18:16:45 -0800 | From | Leonid Yegoshin <> | Subject | Re: [PATCH] Revert "MIPS: Remove race window in page fault handling" |
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(repeat mesg, first one went to wrong place)
Lars,
Do you have a stack trace or so then you found the second VPE between set_pte_at and update_mmu_cache? It would be interesting how it happens - generally, to get a consistent SIGILL in applications due to misbehaviour of memory subsystem, the bug in FS is not enough.
Hold on - do you use non-DMA file system? If so, I advice you to try this simple patch:
Author: Leonid Yegoshin <yegoshin@mips.com> Date: Tue Apr 2 14:20:37 2013 -0700
MIPS: (opt) Fix of reading I-pages from non-DMA FS devices for ID cache separation
This optional fix provides a D-cache flush for instruction code pages on page faults. In case of non-DMA block device a driver doesn't know that it reads I-page and doesn't flush D-cache generally on systems without cache aliasing. And that takes toll during page fault of instruction pages.
It is not a perfect fix, it should be considered as a temporary fix. The permanent fix would track page origin in page cache and flushes D-cache during reception of page from driver only but not at each page fault. It is not done yet.
Change-Id: I43f5943d6ce0509729179615f6b81e77803a34ac Author: Leonid Yegoshin <yegoshin@mips.com> Signed-off-by: Leonid Yegoshin <yegoshin@mips.com>(imported from commit 6ebd22eb7a3d9873582ebe990a77094f971652ee)(imported from commit 0caf3b4a1eebb64572e81e4df6fdb3abf12c70
arch/mips/include/asm/cacheflush.h:
@@ -61,6 +61,9 @@ static inline void flush_anon_page(struct vm_area_struct *vma, static inline void flush_icache_page(struct vm_area_struct *vma, struct page *page) { + if (cpu_has_dc_aliases || + ((vma->vm_flags & VM_EXEC) && !cpu_has_ic_fills_f_dc)) + __flush_dcache_page(page); }
extern void (*flush_icache_range)(unsigned long start, unsigned long end);
It fixed crash problems with non-DMA FS in a couple of our customers. Without it the non-DMA root FS crashes are catastrophic in aliasing systems but it is still a problem for I-cache too but much rare.
Unfortunately, it is also a performance hit, however is less than run a page cache flush at each PTE setup. On 12/03/2014 06:03 AM, Lars Persson wrote: > It is the flush_dcache_page() that was called from the file-system > reading the page contents into memory. > > - Lars > >
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